Honeycomb sandwich panels are characterized by their lightweight, high strength and high rigidity, so they are extensively used as structural members of aircraft. To meet the increasing demand for reducing the weight of aircraft, the honeycomb sandwich panel is fabricated by directly bonding the honeycomb to a prepreg without an adhesive. In this method, when the prepreg is heat-cured, the resin in it oozes out and acts as an adhesive for bonding to the honeycomb. Therefore, it is very important for the resin to have high adhesive strength, and at the same time, it must have good composite characteristics, especially high interlaminer shear strength (ILSS), for use as a surfacing material. Nevertheless, it has been difficult to meet these requirements simultaneously, because one characteristic cannot be improved without sacrificing the other. Furthermore, the resin must have a suitable degree of tackiness when fibers are incorporated therein to form a prepreg.